Einar Sagstuen competed at the 1976 Winter Olympics as a cross-country skiier, entered only in the 4x10 km relay. Along with Pål Tyldum, Ivar Formo, and Odd Martinsen, Sagstuen helped Norway to a silver medal. Sagstuen skiied the second leg, and moved Norway from third to second place with the fourth fastest second leg. He never won a Norwegian Championship but took silver in the 1975 30 km and bronze in the 1976 50 km. He later ran several building companies, including Sagstuen Glass, together with his sons. He was also active in the management of the local hockey club, the Gjøvik Mammuts.